Effects of Plant Spacing on Light Interception, Growth and Yield of Sunflower (Helianthus annuus L.)

Abstract

Plant spacing is an important factor affecting light interception, and consequently affecting plant growth and yield. The objective of this experiment was to study the effect of plant spacing on light interception, growth and yield of sunflower. The experiment was carried out using split-plot in RCB with 3 replications. The main plot consisted of two sunflower cultivars, Pacific 77 and Jumbo. The sub-plot consisted of there plant spacings namely 75x15. 75x25, and 75x35 cm. The study was conducted in the experimental field of Agronomy Department, Faculty of Agriculture, Kasetsart University, Kamphaeng Saen campus, Nakhon Pathom province during November 2007 to February 208. It was found that light interceptions wee significantly different between the two sunflower cultivars and among the three plant spacings. At 75x35 cm plant spacing, light intercepted by sunflower plants was the highest causing the highest growth and development, especially leaf number, leaf area and stem girth. Whereas at 75x15 cm plant spacing, light intercepted was the lowest causing the greatest stem elongation and the smallest stem girth, thus introducing the highest plant lodging percentage in both cultivars. Furthermore, the results indicated that sunflower plants at 75x35 cm plant spacing had the largest head and the highest stem, leaf, head, and seed dry weight in both cultivars while those at 75x15 cm plant spacing had the smallest head and the lowest stem, leaf, head, and seed dry weight. The results also suggested that at 75x35 cm plant spacing which gave the highest light interception, both sunflower cultivars had the highest seed weight per head and the highest yield. On the other hand, the lowest light interception was obtained at 75x15 cm both sunflower cultivars had the lowest seed weight per head and the lowest yield.